1. Field of the Invention
The present invention relates to an internal member of a plasma processing vessel; and, more particularly, to an internal member of a plasma processing vessel, for example, a deposition shield, an exhaust plate, a focus ring, an electrode plate, an electrostatic chuck, an inner wall member of a processing vessel and the like, for use in a plasma processing vessel in which a plasma atmosphere of a processing gas including a halogen element is formed.
2. Description of the Related Art
Processes of manufacturing a semiconductor, a liquid crystal device and the like generally employ a plasma process using a plasma, wherein an internal member of a processing vessel tends to be considerably corroded and worn out because a gas including a halogen element, e.g., a fluoride such as C4F8 or NF3, a chloride such as BCl3 or SnCl4, and a bromide such as HBr, is used in the processing vessel. Therefore, strong plasma resistance is needed in internal members of the plasma processing vessel, such as a deposition shield, an exhaust plate, a focus ring, an electrode plate, an electrostatic chuck, an inner wall of the processing vessel and the like.
In conjunction with this, there is disclosed a technique for improving plasma resistivity of the internal member of the processing vessel by forming a thermally sprayed film with a highly corrosion resistant material such as Al2O3 or Y2O3 on a surface of a base material made of Al, Al alloy, Al oxide, quartz or the like (see, e.g., reference patent 1). Further, an anodic oxidized film may be formed between the base material and the thermally sprayed film. Furthermore, in order to improve adhesivity of the thermally sprayed film, the surface of the base material or the anodic oxidized film can be roughened intentionally by using blast processing or the like to prevent the thermally sprayed film from being peeled off by anchor effect.
In case of the above-mentioned plasma etching processing apparatus, cleaning by a cleaning fluid of pure water, fluorine-based solvent or organic solvent such as acetone is performed on a regular basis to remove a reaction by-product attached to inside of the processing vessel in addition to using the processing gas including a highly corrosive halogen element. In this case, the processing gas and the cleaning fluid for cleaning may permeate into a space between the base material and the thermally sprayed film or between the base material and the anodic oxidized film to thereby generate a corrosion by-product on the surface of the base material by reaction of the gas and the cleaning fluid, resulting in peeling off of the thermally sprayed film.
In other words, in an internal member of a plasma processing vessel 100, as shown in FIG. 21A, a reaction by-product 103 such as CF polymer is deposited on a surface of a thermally sprayed film 102 on a base material 101 such as Al, but the reaction by-product 103 is removed regularly or irregularly, as shown in FIG. 21B among FIGS. 21A to 21D, by immersing it in a given cleaning fluid 104 or by another method. Then, as shown in FIG. 21C, a processing gas, a cleaning fluid, or a fluid reacted with the reaction by-product infiltrates into air pores of the thermally sprayed film 102, a boundary between the sprayed film 102 and the base material 101, or a portion damaged by plasma, the gas and the like to reach the surface of the base material 101. The aforementioned phenomenon is considered to cause the corrosion by-product to be formed on the surface of the base material 101 or the loss of anchor effect by smoothing the surface of the base material roughened to obtain the anchor effect, thus resulting in a portion 105 of the thermally sprayed film 102 being peeled off from the base material 101, as shown in FIG. 21D.
The above-mentioned Al2O3 and Y2O3 have high reactivity on water in the air and when they are used as the inner wall member of the processing vessel and the like, it is possible that a vacuum chamber, the processing vessel, may absorb plenty of water when it is open to the atmosphere or undergoes wet cleaning. And, the abundantly absorbed water in the chamber will be released from the inner wall of the vacuum chamber during process due to high temperature in the vacuum chamber or plasma discharge, which in turn will have adverse effects on the process, such as particle production by chemical reaction of the water with deposits or the inner wall of the vacuum chamber, a prolonged vacuum exhaust time, abnormal electricity discharge, and deterioration of film forming properties.
In this regard, reference patent 2 discloses a method for performing the vacuum exhaust in a short time, wherein a plasma produced is made to contact with the inner wall surface of a plasma producing chamber during a vacuum exhaust process in such a way that temperature of the inner wall is raised to thereby vaporize the adhered water molecules. Further, in reference patent 3, there is presented a technique in which a heater is installed in a lid member of a vacuum chamber and controlled to keep an inner wall of the vacuum chamber at a specified or at a higher temperature all the time during plasma treatment, so that the amount of water and organic matter adsorbed to the inner wall of the vacuum chamber is reduced and, at the same time, the adsorbed water and the organic matter are rapidly vaporized. Furthermore, in reference patents 4 and 5, there is offered a technique in which a removable shield member is installed on an inner wall of a vacuum chamber and instruction for cleaning and replacement of shield member is indicated when the time needed to reach a vacuum state exceeds a set time.
The techniques of the reference patents 2 to 5, however, cannot give a fundamental solution to the problems and the effect thereof is limited since all of them are dealing the situation after water is adsorbed.
reference patent 1: Japanese Patent Laid-Open Publication No. 8-339895 (page 3, FIG. 2)
reference patent 2: Japanese Patent Laid-Open Publication No. 8-181117
reference patent 3: Japanese Patent Laid-Open Publication No. 11-54484
reference patent 4: Japanese Patent Laid-Open Publication No. 11-54487
reference patent 5: Japanese Patent Laid-Open Publication No. 2002-124503